Ruin ground by injecting phosphorous (5)

I believe the answer is:

spoil

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'ruin' is the definition.
(I know that spoil has the is a more specific form of the action ruin)

I don't understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for spoil that I've seen before include "Treat with excessive kindness" , "Wreck" , "Waste from mining; mar" , "Earth from excavation" , "Harm or destroy" .)

I've seen this clue in The Irish Times.

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